Spleen extracts from mammals have been used successfully for years as medical immune modulators. However, the molecular composition of such extracts is unknown and therefore the exact pharmacological actions of these extracts cannot be identified. The dosage response function also cannot be accurately titrated because of the intrinsic heterogeneous nature of these extracts. Because of such heterogeneity, active ingredients in spleen extracts cannot be singled out and their pharmacological actions cannot be fully utilized. And, no matter how careful the extraction process can be, there is always the possibility of transmission of diseases of animal origin to human if animal tissue is used as the raw material for extraction.
U.S. Pat. No. 3,992,364 to Kuhlmey describes a physiologically active polypeptide produced from an animal spleen extract. The exact sequence of the peptide was not disclosed and the preparation was described as being useful for decreasing cholesterol levels and increasing the 17 keto-steroid elimination of human patients.